Unbadrea (ウンバデレイアー Unbaderia) is an amphibious dinosaurian monster who appeared in Ultraman S: Element One, terrorising the seaside port of Chiba in the middle of the night. It was also the first Kaiju Ultraman S fought in the series.

Unbadrea rose from its supposedly "eternal" slumber, disturbed by several underwater submarines carrying out patrols, and started heading towards the sleepy city of Tokyo. Numerous fighter jets were deployed continuously by the Japanese Military Headquarters and supported by the previously defunct CREW GUYS main base to face the monster in combat. However, to no avail, the fighter jets were either plumetted or electrified down one by one, pilots only escaping by the skin of their teeth through ejection.

Unbadrea, looking unaffected, then destroyed several homes and buildings in its vicinity, while the territorial emergency evacuation alarm was sounded. A ball of light then descended from the sky, revealing the giant Ultraman S, who then proceeded to deflect the monster's attacks with ease, in an attempt to calm it down.

However, the weakened Unbadrea was hit by a blast of jet black gusts, transforming it into its terrifying, deformed but yet evolved form: Corrupted Unbadrea. However, the colossus of light managed to beat down and crush the monstrousity with no effort, with no choice but to eventually destroy it with the Crossia Ray.